Abstract
AbstractThis study evaluated the temperature and photoperiod requirements of spawning in ovary‐mature red swamp crayfish Procambarus clarkii and examined the feasibility of inducing spawning in them by inexpensive and practical, nonhormonal treatments. In a spawning induction experiment lasting 20 d, four water temperature gradients (12–14°C, 16–18°C, 20–22°C, 24–26°C) and four photoperiods (completely light [CL], 16 h light: 8 h dark [16L:8D], 12 h light: 12 h dark [12L:12D], and completely dark [CD]) were evaluated. Spawning in ovary‐mature red swamp crayfish could be observed in a relatively broad temperature range, from 16°C to 22°C. A period (5–14 d) of low temperature (16–18°C) significantly induced spawning in ovary‐mature females (p < 0.01), but hibernation began to occur and spawning could not be observed when the temperature was below 14°C. Spawning occurred in both CD and CL circumstances, but long‐period light‐groups showed a higher spawning rate—68.9 ± 10.2% (mean ± SD) for CL and 69.6 ± 6.4% for 16L:8D—than that in short‐period light‐groups—53.3 ± 5.7% for 12L:12D and 33.3 ± 8.3% for CD (p < 0.05). In another spawning induction experiment lasting 3 d, eyestalk interventional stimulating with a high concentration of Na+ combined with a low concentration of Ca2+ induced spawning with a high survival rate (SR = 95.8 ± 7.3% [mean ± SD]) in ovary‐mature females. A high concentration of K+ combined with a high concentration of Ca2+ caused no spawning and a high mortality rate (SR = 20.8 ± 19.0% [mean ± SD]). In this study we also observed that water removal or removing from water can be a stimulating factor of inducing fast and synchronous spawning in ovary‐mature crayfish, inducing 46 (16.0%) of 288 ovary‐mature red swamp crayfish spawned in 10–185 s.
Published Version
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